Geology and hydrogeology Resources (Department of National Resources 1976), the Water 2000 Study (Department of Resources and Energy 1983) and the 1985 Review of Australia's Water A. Laws Resources (Department of Primary Industries and Energy 1987).
Most other reports on groundwater in the area are Introduction unpublished reports covering work carried out to locate water supplies for individual pastoral leases, This section of the report outlines the geology and the Main Roads Department, and town water hydrogeology of the area. Its purpose is to provide a supplies, operated by the Water Authority of Western description of the origin and nature of groundwater Australia. Other unpUblished reports review the water resources within the survey areaf and a practical supplies for the towns of Mt Magnet, Cue, and guide to where they may be located, their salinity, and Meekatharra. general guidelines on how they may be developed. For assistance on the siting of bores or any particular supply, pastoralists and other land users should contact the Director, Geological Survey of Western Australia, Department of Minerals and Energy. Physiography The pastoral industry is one of the major users of The Upper Murchison River Catchment is part of groundwater in the area. Because there is a regional the drainage basin of the Murchison River, and is water-table, and over more than 60% of the total area situated in the Yilgarn Craton (previously termed the the water-table is less than 15 m below ground level, Yilgarn Block) of Western Australia. more than 2000 bores and wells have been constructed throughout the area. However, the distribution of The major physiographic features are shown in stock bores and wells does not reflect solely the Figure 22. Most of the drainage in the area covered by availability of groundwater, but also the different this report, falls within the south-east corner of pastoral value of the land for stock, and its carrying Jutson's (1950) Murchisonia, and drains towards the Indian Ocean. A small, south-eastern part of the area, capacity. is in Salinaland, which drains inland into salt lakes, Consequently bores and wells tend to be more such as Lake Austin. concentrated on areas of alluvium rather than in the thinner, topographically higher, colluvial soils, or in Within the area of Murchisonia there is a marked areas of bedrock outcrop. difference between the topography formed from bedrock of Phanerozoic and Archaean age. Phanerozoic sedimentary rocks occur in the north west of the area, and topographically the area is Previous investigations generally monotonous and flat. There are scattered low hills and a few isolated mesas of duricrust, which Detailed comments on previous geological are more or less overlain and surrounded by sand plains. investigations are given in the relevant 1:250,000 Dunes and playas occupy a broad palaeodrainage in Explanatory Notes (Belele-Elias 1982, Byro-Williams the Yarra Yarra Creek area (Figure 22). In general, 1.R. ef a1. 1983, Cue-De La Hunty 1973, Watkins ef al. areas of high and low relief are related to structural 1987, Glenburgh-Williams S.J. ef a1. 1983, Glengarry features within the Phanerozoic bedrock. Elias ef a1. 1982, Kirkalocka-Baxter ef a1. 1983, Murgoo Baxter 1974, Robinson Range-Elias ef a1. The Archaean terrain is characterised by very 1980, Sandstone-Tingey 1985, and Yalgoo-Muhling shallow alluvial 'valleys' which, to an observer on the ground are so broad and so gently inclined as to ef al. 1977). In 1990 a major report on the geological evolution and mineralisation of the Murchison appear to be flat plains between distant hills. The hill Province was published (Watkins and Hickman 1990), ranges are often flanked by stony pediments which whilst the adjoining Western Gneiss Terrane was shed run-off onto very broad sheetwash plainS. Above mapped in detail by Gee ef a1. (1981, 1986) and Myers the pediments are low rocky hills of bedrock, or (1988). Summaries of the geology can be obtained breakaways over deeply weathered, duricrust-capped from Memoir 3 (Geological Survey of Western bedrock, which lie on the interfluves or at the heads of the main drainage lines. The duricrust remnants are all Australia 1990). that remain of a once continuous Early Tertiary Apart from brief early reports on water supplies for lateritic surface, which has become eroded during mines and batteries in the area (Maitland 1908, Clarke Quaternary times. 1916, and Ellis 1936a, 1936b, and 1953) and later The topography over the areas of outcrop varies reports that concentrated on groundwater in the according to the rock type. The granitoids typically calcrete drainages (Sanders 1969a, 1969b, 1971, 1973a, form large monoliths and extensive uplands of flat 1973b) regional reports on groundwater are limited to pavements, whilst basalt generally produces rugged, Berliat (1957); Morgan (1965); and Baxter (1972). rounded hills. Prominent strike ridges are formed Broadscale regional assessments were made of the from outcropping iron formation and metaperidotite, groundwater resources of this and surrounding areas while felsic volcanics tend to produce gently as part of the 1975 Review of Australia's Water undulating plains.
21 80 km
Sheet calcrete l0J~ Rock outcrops and fringing scree slopes D Main drainage and associated flood plains I??I~H Colluvial arid alluvial sheet wash piedmont plains
6-~::-~J Saline lakes M:m~W~m:1 Sand plain
000 0 0 Drainage basin boundary Physiographic division
Figure 22. Physiographic provinces and units in the survey area.
22 The south-east part of the study area falls within (Watkins 1990, Watkins and Hickman 1990). To the Jutson's Salinaland, and is dominated by a generally north, north-west, and west the Murchison Province is flat to gently undulating topography, with sandy in tectonic contact with the Narryer Gneiss Complex surfaced Quaternary plains. Drainage is to the south of the Western Gneiss Terrane (Myers 1990), whilst to east into saline lakes. The physiography of the eastern the north-east the granite-greenstone rocks are part of the area, and land further to the east is overlain unconformably by sediments of the Nabberu described in Mabbutt (1963). Basin. In the north-west sediments of the Carnarvon Basin occur (Figure 23). The generalised stratigraphy is slUnmarised in Table 4, and the geology and structure in Figure 24. Drainage More than 80% of the drainage in the area is exorheic, draining to the west into the Murchison, Wooramel, and Greenough River catchments, and subsequently to the Indian Ocean. The remainder of Stratigraphy and structure the area has an endorheic drainage system to inland The area underlain by the Murchison Province salt lake systems. consists of a series of greenstone sequences and suites of granitoids. To the north and north-west these abut All drainages are ephemeral. The Murchison River the N arryer Gneiss Complex, which consists of two is very intermittent, but may flow for long periods groups of gneisses. In the north-east and west, these after heavy rainfall. Generally the major drainages rocks are overlain by Proterozoic sedimentary rocks, have broad flood plains, some of which have been and further to the west are unconformably overlain by discontinuously incised by narrow channels. Penman sediments. In the western part of the shldy area, the bed of the Murchison River follows a more deeply incised The greenstone belts trend NNW to NNE, and are sinuous course and is probably a fault-controlled surrounded by the more extensive granitoid subsequent stream along this stretch. Williams I.R. et intrusions. They are shown on Figure 23 as al. (1983) noted the unusual junction of the Roderick undifferentiated mafic and ultramafic rocks, consisting and Murchison Rivers and relate this to a fault of basalt, amphibolite, gabbro and dolerite. They have controlled dam near the junction of the rivers, which been deformed by large scale foldmg and are dissected has been subsequently breached. The west-flowing by faults. Most of the belts occur in the east and south tributaries of the Murchison River and the upper part east of the study area. of the river itself are consequent streams. The granitoid rocks show variable composition and Elongate and dissected sheets of valley calcrete texture, and include biotite granite, muscovite granite, occupy parts of the trunk drainages (Figure 22), and tonalite, adamellite, granodiorite, and granophyre. some are 1 to 2 m or more above the present ground They intrude the greenstone belts and are widespread level, indicating that there has been widespread in the western and central part of the area. erosion of the calcrete since its formation. Further to the east the trunk drainages of the Yalgar and Hope The Narryer Gneiss Complex consist of rnigmatite, Rivers follow probable palaeodrainage lines gneiss, schist, and quartzite of Archaean age, and have developed on the duricrust during the early Tertiary been derived mainly from granite and, to a lesser (Elias 1982). extent, metasediments, dykes, sills, and layered intrusions. On the southern boundary of the complex, To the south-east the palaeodrainage system is between the Whela and Murchison Rivers, schist and represented by saline drainages and salt lakes, with metasediment of the Jack Hills Group crop out as a gypsiferous mud flats and small parabolic banks of prominent linear range. calcareous and gypsiferous sands, surrounded by sand sheets, salt flats, and sheets of calcrete. Lower Proterozoic sediments of the Glengarry Sub basin of the N abbern Basin occur in the north-east where they unconformably overlie the Archaean basement, whilst Late Proterozoic sediments of the Regional geology Badgerrada Group occur as a small intracratonic basin in the western part of the area, overlying Archaean basement, and abutting Permian sediments of the General features Carnarvon Basin. For the purpose of this report the geology has been summarised and simplified, on the basis of its The Permian sediments of the Carnarvon Basin hydrogeological significance (Figure 23). consist of a series of sandstone, conglomerate, siltstone, claystone, and carbonaceous shale, and some Most of the area falls within the Murchison glacial erratics. The sediments rest unconform~bly on Province, which is the westernmost of three granite the Archaean bedrock in a down-faulted synclmal g~eenstone terranes in the Archaean Yilgarn Craton zone known as the Byro Sub-basin.
23 Figure 23: Generalised geology of the survey area.
QUATERNARY
• Alluvium
D Colluvium
trrr~:m L~edepo sh
TERTIARY
• C ....ertlt
PERhtAN
BUMU~fft~n~Jltd
LATE PROTEROZOIC
• Badge,add l Group
EARLY PROTEROZOIC ~ Padbu ARCHAEAN II Undirrertnlial t d gnnitiods Jnk Hils Gr«n$tone BeU Undir'ere"tilted m~r.c • ,,,eIultram afic Undilltrtntilted gneiss •BJ an d migma!il! 30kms 1 I Cainozoic deposits of Tertiary and Quaternary age playas, particularly within the main palaeodrainage overlie much of the area. In Figure 23 the deposits systems. have been simpli fied and grouped together. These deposits have formed in valley, hill slope, hilltop, and Colluvial and alluvial debris have been grouped breakaway environments. together as slopewash deposits in Figure 23. The sediments are erosional products of the bedrock and Within the valley environment deposits of Tertiary lateritised duricrust, and grade downslope from scree calcrete have been formed by deposition of calcium slopes to broad, gently sloping sheetwash plains. They and magnesium carbonates 1n solution frOln water in consist of poorly sorted sand, sil t, and rock fragments, the lower reaches of the catchments. The margins of and are often ferruginised and partly consolidated to the calcrete in terfinger with, and are often overlain by form red-brown hardpan. alluvium. The Quaternary alluvium is predominantly a fine to coarse grained quartz sand with layers and Although not shown in Figure 23, laterite and lenses of silt, conglomerate and clay. Although not silcrete are often developed as a capping to the differenti ated in Figure 23, sand, derived from river weathered profile of bedrock in the area, and are alluvium and erosion of older rocks, forms drifts sometimes preserved as mesas and breakaways along within some of the valleys. Saline alluvium and the major drainage di vides. In many parts of the area gypsifero us sands and clays form large claypans and they are overlain by sheets of sand. 115"30' : 'cAR'NARvoN' ::::: ~~.~!t:'.: :" 1 I GB l00km I:: : :: :: I Carnarvon Basin ~ Nabberu Basin I!){}d Narryer Gneiss Complex I B:I Murchison Province and Greenstone Belts f.:.::"• •:. j Badgeradda Sub-basin [ .,...; I Jack Hills Greenstone Belt Figure 24. Structural geology of the survey area. 25 Table 4. Generalised stratigraphy Age Name Lithology Distribution Quaternary Alluvium Fine to coarse~grained quartz sand, with Creek beds, and major drainage lines. patches of clay, silt, and conglomerate Colluvium Rock fragments, sand and silt Scree slopes to outwash plains and flats along rivers. Lake deposits Clay, silt and grit, some saline to Salt lakes and clay pans, with marginal gypsiferous; eolian sand banks sand banks. Tertiary Calcrete Sheet calcrete Around lakes and in major drainages. Laterite* Massive and pisolitic duricrust Capping to granitoid rocks. Silcrete* Siliceous duricrust Capping to granites and greenstone belts. Permian Undifferentiated Sandstone, siltstone, shale, limestone, and Sediments of Byro Sub-basin of the glacial tillites, some coal measures Carnarvon Basin. Late Proterozoic Badgeradda Group Siltstone, sandstone and conglomerate Small intra-cratonic basin, overlying Archaean gneisses. Early Proterozoic Padbury Group Shale, BIF, dolomite, siltstone, phyllite and Unconformable over Glengarry Group in conglomerate Glengarry Sub-basin. Glengarry Group Quartz arenite, micaceous siltstone Unconformable over Archaean bedrock. Archaean Granitoids Adamellite, granodiorite, biotite granite, Small to large bodies throughout area. tonalite Jack Hills Greenstone Quartzite, conglomerate, schist, Linear outcrop as Jack Hills Range Belt amphibolite, pyroxenite, and peridotite Mafic and Ultramafic Basalt, schist, amphibolite, gabbro, Forms the major greenstone belts in the rocks (Undiff) dolerite, serpentite pyroxenite and south-east of the area. peridotite Migmatite and gneiss Biotite gneiss and migmatite, paragneiss, Forms the Narryer Gneiss Complex in (Undiff) schist, quartzite, and amphibolite west and north-west of area. * Not shown on Figure 23. Hydrogeology Source of data Data have been obtained from the detailed bore General censuses carried out during regional geological mapping in the 1970s and 1980s. More than 2000 bores The area covered by this report places great reliance and wells were sampled, and there is a relatively even on groundwater. It is an area of low rainfall with an distribution of bores and wells throughout the area erratic seasonal distribution, and a high potential (Figure 25). The available bore data (water levels, evaporation; it has, therefore, a general surface water depths, yields, and salinities), are held by the deficiency. Most of the rivers flow after heavy rains Geological Survey. and permanent pools are generally restricted to the Murchison River. Large, semi-permanent pools and waterholes occur along the Roderick, Sanford, Groundwater occurrence Woorame!, Whela, and Yalgar Rivers, and ephemeral water lies for some time after rainfall in many of the Groundwater is generally readily available larger claypans in the region. Small rock holes, throughout most of the area, although quality and probably originating as weathering cavities, occur on quantity vary considerably depending on bore or well the crests and margins of granitoid domes, and in the location. Table 5 summarises the range of bore depths, breakaway areas, but provide supplies of limited yields, and groundwater salinities for the various rock quantity and duration. Before European settlement of types of the three major aquifers i.e. surficial, the area, the Aboriginal population was evidently seclimentary, and fractured rock aquifers. Figure 26 heavily reliant on such sites. diagrammatically shows the relationship of groundwater within the various rock units, and It Groundwater is now used for many purposes. is typical bore locations. essential for the pastoral industry, but is also used for domestic purposes on each pastoral lease, and Over most of the area, domestic and stock water provides town water supplies for Mt Magnet, Cue, requirements are met from small supplies of fresh to and Meekatharra. In addition, groundwater of brackish groundwater in colluvium, valley-fill variable quality is extensively used in the mining alluvium, and calcrete and calcreted alluvium. The industry during the processing and washing of ore extensive wash plains, generally underlain by and tailings. hardpan, that flank the main trunk drainages, provide 26 a reliable source of shallow, good quality groundwater, type, with salinities generally being higher in areas of although groundwater salinity tends to increase closer greenstone than in the granitoids. to the Inain drainage lines. Larger quantities of groundwater are obtainable from the more permeable In the north-east of the area, small supplies of calcrete, and valley-fill alluvium, in the main trunk variable, but generally fresh to brackish, water may be obtainable from the Proterozoic sandstones and drainages. fractured banded iron-formation (BIF) of the Nabberu Further from the drainages, smaller supplies can be Basin. Similar supplies may be obtained from the obtained from the colluvial hills lope wash, adjacent or Proterozoic sediments of the Badgeradda Group in the marginal, to rock outcrop, and also from the west. Further to the west and north-west, within the weaJhered bedrock profile, and from fractures and Carnarvon Basin, the sandier sections of the Permian shear zones within the fresh bedrock. Yields are small, sediments yield reasonable quantity and quality and quality tends to vary in relation to the bedrock groundwater. Table 5. General range of depths, salinity, and yields of bores Aquifer Bore depths (m) Water levels (m below Salinity range (mg/L Supply range ground surface) TDS) (m'/day) Surficial Calcrete 5-30 0-5 250-12,000 50-1,000 Alluvium 5-35 0-5 400-12,000 50-200 Colluvium 10-30 5-15 800- 6,000 20- 100 Sedimentary rocks Permian > 100 > 80 700- 3,500 50-250 Late Proterozoic 30-60 5-20 2,000- 9,000 50- 100 Early Proterozoic 30-60 5-15 1,000- 2,000 5- 100 Fractured rocks Granitoids 5-45 5-40 500- 4,000 10- 50 Gneisses/migmatites 10-50 5-45 2,000- 7,000 5- 10 Greenstone belts 30-100 20-40 1,000- 4,000 100-2,000 '" 60 km .~. Bores, wells ~ River, creek Road ------Track - / - Rabbit Proof Fence Figure 25. Bores and well s in survey area. 27 ~ NARRYER MURCHISON PROVINCE COMPLEX ...... ': t . ...... ----...... , ...... +++ ...... J- ...... ; .. ...... +'~';""+':'+';'''';1'~'+'+'~''':''';>';'''~'''''''''''''''''''''...... , ...... +++ + +.++++++++ ++ ...... ++ .... ++ ••• .... +. + ..... ++ ...... ++++ ..... + ...... +.+ + ...... •••• + ...... ++ ...... gneisses and migmatites granitoids limit of w.eathering V ' + greenstone belt ++++++ N 00 Typical bore locations CARNARVON Badgeradda Sub-basin NABBERU BASIN BASIN i Late Proterozoic sedimentary rocks ...C2~~~ -.~ I f +, ' '+ ...... f . ~'...... t· ,'...... ++ •• I f f f Permian I f sedimentary gneisses and mIgmatites granitoids .. g;aniioids rocks Figure 26. Relationship of groundwater within various rock units and typical bore locations. Fi gure 27. Water·table map of the survey area. Bedrock highs ~ - ... "'... Zone for How through calcullltioJl (See Table 6) ~ Water1able contour (m AHD) ~ River, Creek __ Geooralized How dirsction -- - - Track ...... Sub-ealchment boundary Reg ional water-table and water-table ~ RabbltProof f ence SutJ.-catchmefli (See Table 6) levels The determination of the groundwater flow systems in the study area is based on hydrogeological data to under 260 m in the west, a drop of more than 240 m collected during regional geological mapping, in about 300 km, equivalent to a gradient of 1 m per supplemented by data obtained from town water 1250 m. supply investigations, exploration for water supplies Interpretation of the water-table contours (Figure for milting purposes, and from bores drilled for road 27) shows a series of smaller sub-catchments to the construction water supplies. Consequently the data main Murchison Ri ver catchment, and other are non-synoptic. catchments. A total of 13 sub-catchments are shown, In addition the bores and wells have not been 12 exorheic and 1 endorheic (Table 6). Of the 12, 7 are surveyed to Australian Height Datum and wa ter-table either catchments to tributaries of the Murchison elevations have been calculated from estimates of River, or to part of the river itself. Two of the sub surface elevation from 1:100,000 topographic series catchments contribute to the Wooram el Ri ver maps. catchment in the north-west, one to the Greenough River in the south-west, and two to the Mongers Lake The water-table map (Figure 27) and the depth-to system to the south. The endorheic sub-catchment is water map (Figure 28) are therefore generalised, and centred on Lake Austin in the south-east of the area, should be used with caution for future drilling and into which groundwater drains and discharges by groundwater exploration. Salinity has been evapotranspiration. determined mainly in the field using conducti vity measurements, and may also vary seasonally. Most of the sub-catchments are linear, with the Consequentl y the salinity data in Figure 29 are also drainage line forming the main axis. They range in generali sed. size from less than 2600 km' to more than 13,750 km'. Hydraulic gradients along the main axes are very low Whilst there are limited water supplies in areas of and range from 0.6 to 2.6 x 10" . bedrock outcrop, or near outcrop, it is evident that a regional water-table exists throughout the study area The depth to the water-table (Figure 28) ranges from (Figure 27). The height of the water-table ranges from less than 1 m to over 80 m in the extreme west of the over 500 m AHD on the eastern boundary of the area, area, in the Carnarvon Basin. In most of the area the 29 16602-3 ;;; depth to water is generally less than 15 m. All areas ;; with a water-table deeper than 20 m are shown as one B• L ~ subdiv ision. c a.w w u u. The depth to the water-table is closely re lated to 13 ~w 13e E topography, parti cularly on the Yilgarn Craton. Water E E , 0• "- E E • 0 ~ u 15 levels are deepest beneath the catchment divides ~ 0 ~ ~ 0 ~ Oi D I N 0 > ~ •0 '"0 ~ , ~ 0 0: 0:• where bedrock crops out or is close to the surface, and 0 '" ii' r- shallowest in the drainage lines, where grow1dwater discharges to the sub-surface and pools in the watercourses. D I I I \ ~ ~ Figure 28. Depth to water-table within the survey area. 30 Groundwater resources Throughflow There are insufficient controlled data to enable a Calculation of throughflow in the sub-catchments is detailed assessment of groundwater resources in the based on the Darcy equation: study area. An approximation of the resources can be Q Kdil provided based on a range of estimates of various . hydrogeological parameters. Estimates have been where: made of the likely amount of recharge to the area from rainfall, the amount of groundwater flowing through Q throughflow (m'l day); each sub-catchment (Figure 27), and the amount of groundwater stored in each sub-catchment. The K hydraulic conductivity (ml d); estimates are given in Table 6 and should be regarded d saturated thickness (m); as only a guide to the likely amounts of water within hydraulic gradient (dimensionless); the area. width of throughflow zone (m). Recharge Of these parameters i and I can be measured from the water-table contours in Figure 27, and d can be Groundwater recharge is from rainfall, which in the estimated from bore or well data. However, K is study area ranges from 200 to 250 mm per annum. unlcnown, and can only be estimated on the basis of Recharge over the area has been estimated from an the rock type. established data set (Department of Primary Industries and Energy 1987), on the basis of 0.005% of The throughflow zone will not be a constant rainfall for areas underlain by fractured bedrock and thickness across its total width; nor will it have the related material, and 0.1% for the remainder of the same hydraulic conductivity. Groundwater flow will area. Total direct recharge from rainfall averages about be concentrated within the more permeable alluvium 12 x 106 m' per armum (Table 6). Recharge may take and calcrete, and total throughflow will diminish place over the whole of each catchment, although further upslope towards the drainage divides. where the water-table is shallow and in discharge Estimates of throughflow, given in Table 6, have areas with upward heads it may be insignificant. been derived by adopting the following assumptions Similarly, whilst recharge on areas of bedrock for saturated thickness and hydraulic conductivity. outcrop may be small, these areas are nevertheless The width of the calcrete I alluvium section of the important in providing run-off concentrating recharge water-table contour over which the throughflow has further downslope. Further recharge of the alluvium been calculated was estimated from Figure 23, and and calcrete in the drainage lines occurs from stream assumed to have a saturated thickness of 20 m and a flows after heavy rains. hydraulic conductivity of 2.5 ml d. The remaining section of the contour, underlain by colluvium and The contours in Figure 27 indicate that all of the bedrock, was assumed to have an average saturated exorheic sub-catchments discharge to the stream line, thickness of 10 m and a hydraulic conductivity of 0.5 whilst the endorheic sub-catchment discharges to Lake mid. The thicknesses were adopted to allow for the Austin. presence of saturated weathered bedrock. Table 6. Groundwater resources Evapotranspiration Sub-catchment Storage and discharge Area Rainfall Recharge Through flow No. Name 2 (mm) 3 6 3 6 (km ) (m x 10 /a) (m x 10 /a) (m3 x 106/a) (m3 x 109) Greenough 4,500 250 0.48 0.24 0.24 0.13 2 Mongers 1 2,600 250 0.22 0.11 0.11 0.52 3 Mongers 2 3,540 225 0.57 0.52 0.05 0.10 4 Sanford 9,200 225 1.06 0.39 0.69 0.50 5 Roderick 5,350 225 0.75 0.22 0.52 0.29 6 Whela 6,050 200 0.87 0.36 0.51 0.48 7 Hope 10,540 200 1.21 0.46 0.75 0.84 8 Yalgar 4,425 200 0.63 0.37 0.26 0.24 9 Murchison 1 8,600 200 0.72 0.59 0.13 0.81 10 Murchison 2 7,700 225 1.16 0.82 0.34 0.80 11 Wooramel 3,925 225 0.55 0.42 0.13 0.21 12 Byro SIB 12,200 225 1.96 0.69 0.97 1.87 13 l. Austin 13,750 200 1.97 1.66 0.31 1.43 12.16 7.05 5.11 8.22 31 Storage towards the drainage lines, particularly the main trunk drainages. The lowest salinity groWldwater The estimation of storage is based on an average occurs along drainage divides where bedrock may be saturated thickness over each of the subcatchments closer to the surface, the water-table IS deep, and and a value for the specific yield of the rock types where the groundwater has the within the catchment. As noted earliel; the average shortestresidenc~ time. Further down the flow paths, and 111 the mam saturated thickness will be greater within the lower drainage lines, the water-table is shallower, and there parts of the catchments, along the drainage lines, is concentration of salts by evaporatIOn, and where thicker sequences of alluvium, calcrete, and transpiration of phreatophytic vegetation. colluvium have been deposited, and will diminish upslope towards the drainage divides. Although the main drainages generally flow with fresh water after heavy rains, stream salinity rapidly In order to derive the figures for storage in Table 6, increases, as surface flow ditninishes and groundwater the area underlain by calcrete and alluvium was discharge becomes more significant. estimated from Figure 23 and assumed to have a saturated thickness of 10 m and a specific yield of 5%. In areas of internal drainage, such as the Lake The remaining area was assumed to be underlain by Austin sub-catchment, groundwater flow is towards a colluvium and bedrock with a saturated thickness of central lake from which discharge is solely by 5 m and a specific yield of 0.1%. The saturated evapotranspiration. In these areas salinity increases to thiclG1esses are less than those taken for the calculation more than 50,000 mg/L TOS. of throughflow, to allow for the thimung of the Examples of some groWldwater analyses from saturated zone higher in the drainage line and selected rock wlits are given in Table 7. Groundwater topography. Thls gives an estimated total throughout the area is generally a sodiwn chloride 9 3 groundwater storage of about 8 x 10 m for the Shldy type, reflecting its derivation through precipitation area. from cyclic salts. Groundwater from calcrete is On the basis of these figures, the estimated amount generally harder than water from other sources of water stored in the area is considerably more than although high levels of hardness have been recorded that discharged from the area, either as throughflow, in water from colluvium, alluvium, and Proterozoic evapotranspiration, or discharge/ abstraction. In the sandstones. short term, annual fluctuations in recharge from the In many cases the groundwaters contain high levels variable rainfall, are unlikely to affect water-table of sulphate, which may relate to nearby levels, particularly in the thicker saturated zones. mineralisation. Nitrate levels are also high throughout However, extended periods of drought are known to the area and beyond the World Health Organisation cause a lowering of the regional water-table. ) standards (45 mg/L as N03 for human consumption (WHO 1971). The source of the nitrate is probably not pollution, though some may come from animal Salinity and quality wastes, but rather nitrate fixation from vegetation or possibly termites (Smith et al. 1990). In addition high During the geological mapping of the 1:250,000 levels of silica are reported from all sources, although sheets covered by the study area, samples of they are not considered harmful. groundwater were collected from all bores or wells that were operative, and field determination of conductivity was subsequently converted to salinity Groundwater availabiiity (as mg/L Total Dissolved Solids - TOS). Some of these samples were also submitted to the Chemistry Centre The data in Figures 27 to 29 indicate that of Western Australia for detailed analysis. Additional groundwater occurs throughout the study area. analyses supplementing the field analyses, include the However, the quantity and quality vary considerably chemical analyses of groundwater from Town Water depending on location and the nature of the aquifer Supplies and from groundwater exploration by and bore/well location (Table 5 and Fignre 26). consultants for mining and mineral processing Regional groundwater contours (Figure 27) indicate requirements. that groundwater flow is controlled by the surface catchments, with groundwater flow towards, and The salinity values frOlll these determinations are discharge to, the main drainage line. At the same time contoured in Figure 29, which shows the distribution the depth to grotmdwater (Figure 28) decreases to the of salinity in the study area. Most of these analyses drainage line, and water quality also decreases were determined between 1972 and 1982, and are (Figure 29) and becomes bracldsh to saline. therefore non-synoptic. However, it is considered that groundwater salinity is wl1ikely to have changed Along the drainage lines, the shallow water-table sigluficantly during the period of the sampling. together with the occurrence of deposits of surficial seditnents results in areas of increased storage and Groundwater salinity in the study area is derived throughflow, and consequently areas where yields frotTI two main sources: cyclic salts from precipitation may be expected to be larger. As a result, the largest over the area, and salts leached from bedrock and the groundwater supplies withln the region are from such lateritic and weathered profiles (Brookfield 1963). surficial formations, although good supplies of water The distribution of groundwater salinity is shown in can be obtained from other rock types depending on Figure 29. On a regional scale, salinity increases local site-specific conditions. 32 I 11700'\ , \ \ I _I,\ 27 00' Figure 29. Distribution of groundwater salinity within the survey area. Salinity (mglL Total Dissolved Sotids) D 0·1000 Surficial aquifers 1000 ·2000 The main surficial aquifers comprise the deposits of 2000·3000 calcrete, alluvium, and, to a lesser extent, colluvium. 3000 ·4000 Calcrete deposits are restricted to drainage lines and may interfinger with deposits of alluvium, and these in turn grade into, or are overlain by colluvium away ______- Contours of depth to water from the drainage lines. ______- -c---~-::c_::._ River, Creek ----Track Road -L- Rabbit Proof Fence Calcrete Calcrete is a carbonate rock formed by the il1 situ 30 km replacement of valley-fill debris by magnesium and calcium carbonate precipitated from percolating carbonate-saturated groundwater (Sanders 1973a). lt has a well-developed secondary porosity and high often fractured and fissured, and water movelnent can permeability, and forms an excellent aquifer. open up the fissures to more than 0.3 m in width. As a result large cavities can be developed, which can lt occurs generally along flat reaches of ancestral or contain considerable volumes of groundwater. Yields existing water courses, and around saline lakes. It in excess of 1000 m'l day can be obtained from crops out as low Inounds separated by narrow alluvial properly constructed bores. drainages. In some areas groundwater in calcrete is very fresh, In areas it is overlain by thin deposits of alluvial and is used for Cue, Mount Magnet, and Meekatharra wash and eolian sand often showing the development town water supplies (AGC 1987a, 1988a, WAWA 1989). of gilgai structures from carbonate solution and soil In other parts of the study area groundwater quality IS collapse. poorer, and salinities in excess of 7000 mg/L TDS are Generally calcrete can range from less than 5 m obtained. Howevel; the poorer qualIty water IS stIll thick to in excess of 30 m, and the water-table is often suitable for Some classes of sheep, for mineral marked by the occurrence of opaline silica, when processing and for water supplies for road salinity is in excess of 5000 mg/L TDS. This layer is construction purposes. 33 The depth to groundwater within calcrete is to remove any fine sand or silt within the aquifer. If generally less than 5 m and total depths of bores do the aquifer consists of very coarse sand or gravel, it not usually exceed 30 to 40 m. Water supplies can best may be possible to construct the bore with machine be developed from bores either equipped with slotted slotted casing, but if the aquifer consists of thin casing, or with a suitable bore screen. The often interbeds of sand and silt, a bore can best be cavernous structure of the material increases the risk constructed using machine slotted casing over the full of pollution, and care needs to be taken in the location saturated thickness, and a suitable gravel pack for the of bores. annular space. Alluvium Colluvium Alluvium occurs in all the main drainages and Colluvial deposits on outwash fans, talus, and scree generally consists of a fine-to coarse-grained quartz slope deposits, occur marginal to bedrock and extend sand, with layers and lenses of silt, conglomerate and downslope to the alluvial-filled drainage lines. The clay. The thickness of the alluvium varies considerably, deposits consist of angular rock and quartz fragments depending on the size and age of the drainage line, in a brown silt and sand. The deposits grade and can range from less than 5 m to about 25 m, and is downslope into broad sheetwash. They border or occasionally thicker (AGC 1987a). Where sand grade into the alluvial deposits. deposits are well developed the alluvium has a high permeability, although the presence of silt and clay The thickness of the colluvium ranges from less than reduces both the permeability and bore yields. 2 m to 15 m. The broad sheetwash plains bordering the alluvium provide a reliable source. The water-table is Groundwater quality is also variable. Figure 29 generally less than 15 m below ground surface, and indicates that, towards the drainage divides, salinities are generally less than 2000 mg/L, but groundwater salinity is low. However, groundwater in increase towards the main drainage lines. There may the alluvium is over 7000 mg/L TDS in the lower also be some quality variation dependent on the reaches of the major drainage lines. underlying bedrock type. Elias (1982) suggests that The depth to groundwater in the alluvium is more saline water occurs in colluvial deposits generally less than 5 m, and total depths of bores and overlying greenstone areas rather than granitoid areas. wells do not usually exceed 25 to 35 m, although depths in excess of 60 m have been noted (AGC The colluvial deposits are generally less permeable 1987b). Water supplies are generally not as large as than the alluvium and calcrete, and consequently water supplies are generally lower. Yields of less than those obtained from calcrete, but location of bore sites 3 in the deeper sections of alluvium, together with 50 m 1day are common, and supplies are generally correct bore construction should enable supplies of 50 better beneath the lower plains than higher on the scree slopes. The poorly sorted nature of the sediments to 200 m'l day to be obtained. result in considerable variation of permeability, and Bores in the alluvium should be constructed using a bores constructed using gravel-packed, fully-slotted suitable stainless steel screen set in the coarsest sand casing, or large diameter wells have the best prospects section, and the bore should be adequately developed for obtaining water supplies. Table 7. Chemical analyses (mg/L) of groundwaters from selected rock units PAT 1 Killer Name Limestone Tree Woolbung Coolardy Deep Homestead 140' Big Bell 3 5 Paddock 1 MYP I' Wellz Well WeW Wella Well1!l G.M.I Well WellS Bore Aquifer Czk Czk Qa Qa Qc Qc SST Ag Gab Gnstne Depth (m) 18.0 4.7 nr 5.3 4.2 5.6 39.6 32.0 66 42.7 SWL (m) 4.0 4.3 17 4.8 3.2 5.1 16.7 nr 20.5 30.5 pH 7.6 8.2 7.9 7.5 8.1 7.0 8.1 7.9 7.9 7.8 TDS 6,940 4,220 2,465 620 7,680 1,040 2,990 645 1,280 3,140 Hardness 1100 823 nr 204 1495 183 668 nr 289 nr Alkalinity 2150 170 nr 80 245 35 115 nr nr nr Ca 110 127 102 29 244 29 101 33 23 85 Mg 200 123 113 31 216 27 101 50 57 118 Na 2,150 1,110 525 186 2,139 243 819 108 300 808 K 65 95 50 15 66 21 42 19 7 39 HCOa 290 207 119 98 299 43 140 76 310 214 CI 3,635 1,946 895 303 3,694 409 1,453 180 380 1,220 SO, 610 402 340 64 711 80 250 65 100 445 NO, 65 32 19 60 47 58 96 21 106 19 Si02 65 65 105 86 75 108 63 58 nr 51 1. Cue sheet 6. Maiangata station Qa: Alluvium Ag: Granite 2. New Forest station 7. New Forest station Qc: Colluvium Gab Gabbro 3. Glengarry 8. Sherwood station Czk: Calcrete Gnstne Greenstone 4. Wooleen station 9. Belele station SST: Proterozoic sandstone 5. Boolardy station 10. Polelle station 34 Sedimentary aquifers Fractured rocks Permian Granitoids The main occurrences of sedimentary rocks are in The granitoid basement rocks consist of even the north-west of the area, where Permian rocks of the grained to porphyritic granite and adamellite, with Byro Sub-basin occur. some granodiorite and tonalite. In places they are deeply weathered to more than 40 m and small A limited number of bores are drilled into these rocks, but existing bore data indicate that groundwater supplies of groundwater may be obtainable from flow is to the west. The depth to water also increases to within, or at the base of the weathered profile. Some the west, and the water-table may be in excess of 80 m. groundwater may be intersected in exfoliation joints in Salinity and quantity vary considerably. Water suitable the upper few metres of the fresh bedrock. However for stock is generally obtainable from the Moogoo100 there is little evidence of bores exploiting this zone, Sandstone, but parts of the sequence (e.g. Lyons and the main source of groundwater appears to be in Group) will yield larger supplies of potable quality the weathered profile. water (Williams LR. et a1. 1983). Allen (1987) reports Where groundwater associated with the granitoids salinity in the Permian rocks ranging from 860 to 1930 is exploited, salinity ranges from 500 to 4000 mg/L mg/L TDS (Moogoo100 Sandstone) and 700 to 3230 TDS, with the lower salinity water occuring along the mg/L TDS (Lyons Group), and indicates that a drainage divides, and increasing in salinity towards complex water-table exists and salinity and yields are the drainage lines. Depths of bores are variable highly variable. depending on the location of the site within the topography, but can range from 5 to 45 m. However, Successful bores may need to exceed 100 m in the the higher in the topography the bore, the more western part of the area, and drilling may need mud likelihood that the supply will be small, and subject to rotary techniques and geophysica110gging to locate large seasonal variations in the water-table levels. optimal positions for bore screens to ensure adequate supplies. Gneisses and migmatites Late Proterozoic Groundwater generally occurs in the weathered profile, which usually has a high clay content. As a In the west, in the Late Proterozoic sedhnentary result salinities range from 2000 to 7000 mg/L TDS, rocks of the Badgeradda Group, groundwater though less saline groundwater can be obtained closer salinities range from about 2000 to 9000 mg/L TDS, to the drainage divides, where salinities may be less with the more saline water derived from shale. Deep than 1000 mg/L IDS. The depth to the water-table Bore (Table 7) is in sandstone and has a salinity of ranges from 12 to 15 m, and supplies are usually less 2990 mg/L TDS. 3 than 10 m / day. Depth to water in the Badgeradda Group ranges from less than 5 m to more than 20 m below ground Greenstone belts surface, depending on topography and bedrock type. Bores depths may range up to 60 m and future site Drilling in the search for water for mineral selections should be aimed at locating drilling targets processing, has mainly been on highly fractured and in sandstone, particularly where strong fracturing sheared zones in basalts and dolerites, some of which and/ or jointing occurs, and recharge has been extend more than 100 m below ground level. enhanced. The sandstone should be competent enough Bores have been drilled to depths greater than 100 m to allow slotted casing to be used in bore construction, in several areas, but in these deep bores, static water 3 and yields of 50 to 100 m / day may be obtainable. levels range from 20 to 40 m. A wide range of yields, 3 between 100 to 1800 m / day, have been obtained, Early Proterozoic whilst salinity has generally ranged from 100 to 4000 mg / L IDS, although salinities in excess of The Early Proterozoic sedimentary rocks of the 60,000 mg / L TDS have been obtained. Padbury and Glengarry Groups occur in the extreme north-east of the area. Limited bore data indicate that the groundwater in Conclusions this area may be obtained from sandstone and Regionally, the water requirements for the pastoral dolomite sequences, and probably from banded iron industry are generally small, and bore yields seldom formation. The water-table is between 5 m and 15 m 3 exceed 10 m / day, although larger supplies in excess below ground surface, and groundwater salinity of 20 m 3 / day are available in areas of calcrete and ranges from 1000 to 2000 mg/L TDS. Bore yields range thick alluvium. Water quality generally poses little from 50 to 100 m' / day, although better supplies problems as water with a salinity up to 7000 mg/L should be obtainable from fractured sections of the TDS can be utilised by stock. Shallow groundwater banded iron formation. with a higher salinity is generally restricted to the It is likely that, as with the Badgeradda Group, the main trunk drainages. Domestic supplies on pastoral formations should be competent enough to allow leases are usually met from wells or bores, or from slotted bore casing to be used in bore construction. collection of rainwater from roof catchments. 35 On the basis of about 2000 bores and wells, with an Ellis, H.A (1953). Report on underground water supplies in the area 80% utilisation rate, pumping at 5 m'l day, east of Wiluna. Western Australia Geological Survey, Annual groundwater consumption by the pastoral industry is Report for 1951, pp. 9-12. 6 about 2.9 x 10 m'l annum. This is quite small Gee, R.D., Baxtel~ J.L., Wilde, S.A. and Williams, LR. (1981). Crustal compared with the estimated groundwater storage, development in the Yilgarn Block. In: Archaean geology (Eds J.E. Glover and D.l. Groves); International Archaean and even allowing for groundwater discharge by Symposium, 2nd, Perth, WA 1980. Proceeding, Western throughflow and evapotranspiration, there appear to Australia Geological Society of Australia, Special be satisfactory water resources to withstand short Publications, No.7, pp. 43-56. periods of drought. Gee, R.D., Myers, J.S. and Trendall, AF. (1986). Relation between Archaean high-grade gneiss and granite-greenstone terrain in References and bibliography Western Australia. Precambrian Research 33: 87-102. Geological Survey of Western Australia (1990). Geology and Mineral A.G.e. (1987a). Groundwater scheme review-Cue. Australian Resources of Western Australia. Western Australia Geological Groundwater Consultants Pty Ltd. Water Authority of Survey;. Memoir 3. Western Australia, Water Resources Directorate, Report No. WG26. Johnson, W. (1950). A geological reconnaissance survey of parts of the Yalgoo, Murchison, Peak Hill, and Gascoyne Goldfields. A.G.c. (1987b). Big Bell Gold Project water supply, groundwater Western Australia Geological Survey Bulletin 106. investigations (Unpublished report). Jutson, J.T. (1950). The physiography (geomorphology) of Western A.C.C. (1988a). Groundwater scheme review-Mt Magnet. Australian Australia. Western Australia Geological Survey;. Bulletin 95. Groundwater Consultants Pty Ltd. Water Authority of Western Australia, Water Resources Directorate, Report No. Mabbutt, J.A. (1963). Geomorphology of the Wiluna-Meekatharra WG11. area: In: Lands of the Wiluna-Meekatharra area, Western Australia, 1958. CSIRO Land Research Series No.7. Allen, A.D. (1987). Groundwater. In: Geology of the Carnarvon Basin, Western Australia. Western Australia Geological Maitland, A.G. (1908). Artesian water boring in the Murchison, Survey, Bulletin 133. Gascoyne, and Kimberley Districts. Western Australia Geological Survey, Annual Report for 1907, 5 pp. Baxter, J.L. (1972). Regional hydrogeology of the Murgoo 1:250,000 sheet SG / 50-14, Western Australia. Western Australia Morgan, KH. (1965). Hydrogeology of the East Murchison and Geological Survey;. Record 1971/14. North Coolgardie Goldfields area. Western Australia Geological Survey, Record 1965/16. Baxter, J.L. (1974). Murgoo, WA. Western Australia Geological Survey, Explanatory Notes SG / 50-7. Muhling, Ee. and Low, G.H. (1977). Yalgoo, WA Western Australia Geological Survey;. Explanatory Notes, SH/50-2. Baxter, J.L., Lipple, S.L. and Marston, RJ. (1983). Kirkalocka, WA. Western Australia Geological Survey. Explanatory Notes, Myers, J.S. (1988). Early Archaean Narryer Gneiss Complex, Yilgarn SH/SO-3. Craton, Western Australia. Precambrian Research 38: 309-324. Berliat, K. (1957). Report on hydrogeological reconnaissance in the Myers, J.S. (1990). Western Gneiss Terrane. In: Geology and mineral Mul1ewa District. Western Australia Geological Survey, resources of Western Australia. Western Australia GeolOgical Bulletin 112, 22 pp. Survey, Memoir 3, pp. 13-31. Brookfield, M. (1963). Water Supply in the Wiluna-Meekatharra Sanders, c.e. (1969a). Hydrogeological reconnaissance of calcrete area. In: Lands of the Wiluna-Meekatharra Area, Western areas in the East Murchison and Mount Margaret Goldfields. Australia, 1958. CSIRO Land Research Series No.7. Western Australia Geological Survey;. Record 1969/1. Clarke, E. De e. (1916). The geology and ore deposits of Sanders, e.e. (1969b). Hydrogeological reconnaissance of calcrete Meekatharra, Murchison Goldfield. Western Australia areas in the East Murchison and Mount Margaret Goldfields. Geological Survey;. Bulletin 68. Western Australia Geological Survey, Annual Report for 1968, pp.14-17. De La Hunty;. L.E. (1973). Cue, WA. Western Australia Geological Survey;. Explanatory Notes SG/50-8. Sanders, c.e. (1971). Paroo Calcrete hydrogeological investigation interim report. Western Australia Geological Survey, Record Department of National Resources (1976). 1975 Review of 1971/2. Australia's water resources and water use. AGPS. Sanders, e.c. (1973a). Calcrete in Western Australia. Western Department of Primary Industries and Energy (1987). 1985 Review Australia Geological Survey, Annual Report for 1973, pp. 12- of Australia's water resources and water use, Volume I, water 14. resources data set. AGPS. Sanders, e.e. (1973b). Hydrogeology of a calcrete deposit on Paroo Department of Resources and Energy (1983). Water 2000. A Station, Wiluna, and surrounding areas. Western Australia perspective on Australia's water resources to the year 2000. Geological Survey, Annual Report for 1973, pp. 15-26. AGPS. Smith, GD., Lynch, R.H., Jacobsen, J. and Barnes, e.r (1990). Elias, M. (1982). Belele, WA. Western Australia GeolOgical Survey, Cyanobacterial nitrogen fixation in arid soils of Central Explanatory Notes SG / 50-4. Australia. FEMS Microbiology Ecology. 74: 79-90. Elias, M., Bunting, J.A. and Wharton, P.H. (1982). Glengarry, WA. Tingey, RJ. (1985). Sandstone, WA. Western Australia Geological Western Australia Geological Survey, Explanatory Notes SG / Survey, Explanatory Notes, SG/50-16. 50-12. WAWA (1989). Groundwater scheme review-Meekathana. Water Elias, M. and Williams, S.r (1980). Robinson Range, WA. Western Authority of Western Australia, Water Resources Directorate Australia Geological Survey, Explanatory Notes SG/50-7. Report WG 42. Ellis, HA. (1936a). Proposed water supply for Tuckanarra Battery;. Watkins, KP. (1990). Murchison Province. In: Geology and mineral Murchison Goldfield. Western Australia Geological Survey, resources of Western Australia. Western Australia Geological Annual Report for 1935, 13 pp. Survey, Memoir 3, pp. 32-59. Ellis, H.A. (1936b). The location of a bore site for water at Gnaweeda Watkins, KP. and Hickman, AH. (1990). Geological evolution and Station, Meekatharra. Western Australia Geological Survey; mineralisation of the Murchison Province, Western Australia. Annual Report for 1935, 14 pp. Western Australia Geological Survey;. Bulletin 137. 36 Watkins, K.P., Tyler, I.M. and Hickman, A.H. (1987). Cue, WA. Western Australia Geological Survey, Explanatory Notes scI 50-8, 2nd Edition. WHO (1971). International drinking-water standards. 3rd Edition. World Health Organisation, Geneva. Williams, I.R., Walker, LW., Hockin& RM. and Williams, S.J. (1983). Byro, WA Western Australia Geological Survey, Explanatory Noles SG/50-3. Williams, SJ, Williams, lR. and Hocking, RM. (1983). Glenburgh, WA Western Australia Geological Survey, Explanatory Notes SG/51-1. 37 The Survey Methods Field work program As a preliminary to fieldwork, tentative. land . systems and their likely boundarIes were ldentified General approach and marked onto the most recently available (mainly) 1:50,000 scale black and white stereo aerial This survey adopted the land system approach to photographs (Table 8). Published back?,ound . resource description and evaluation, as used for information on geology, landforms, SOlIs, vegetatIOn previous rangeland resource surveys in Western and land system classifications was available from Australia (Wilcox and McKinnon 1972, Payne et a1. several sources. These included the Geologrcal Survey 1979,1982,1987, 1992, Mitchell et al. 1979). of Western Australia (1:250,000 map sheet series), The land system approach to the management of Bettenay et al. (1967), Beard (1976), Payne et al. (1987), rangelands, in Australia and overseas, has withstood Wilcox et a1. (1972) and Mabbutt et al. (1963). False the test of time. This approach maps the component colour images generated from Landsat (multi-spectral lands of extensive arid and semi-arid regions, in a scanner) data were also used to provide broad natural classification at the smallest scale which is overviews of the area. usefully applicable for planning land use, Topographical and pastoral lease infrastructural management and infrastructure design across very features such as roads, fences, tracks and watering broad catchments. points were also identified and marked up on the aerial photographs before fieldwork started. Christian and Stewart (1953, 1968) defined a land system as 'an area or group of areas throughout which The program of field work was carried out between there is a recurring pattern of topography, soil and June 1985 and March 1988, with a total of 32 weeks of vegetation'. Each land system has characteristic fieldwork undertaken by the full team: patterns able to be seen on aerial photographs and other forms of remotely sensed images. Discrete areas Rangeland Advisers P.J. Curry, A.L. Payne of a land system mostly occur in areas greater than Staff SurVeyor K.A. Leighton 5 km' and are therefore of a scale suitable for mapping Navigator /Draftsperson J. Neil at 1:250,000. Land systems consist of a number of Soil Technician P. Hennig (and S.J. Fritz) smaller land units or elements, each of which has a Senior Survey Hand L.J. Merritt distinctive photographic pattern. The relative proportion of the component units and their Botanist RJ. Cranfield (WA arrangement one to another gives the broader three Herbarium) dimensional pattern that characterises the particular land system. The methodology to achieve consistent coverage and assessment of the whole area was designed after Exhaustive effort was made to maximise the five weeks of reconnaissance surveys. Development of objectivity of the assessment of soil and vegetation efficient and appropriate field techniques was the resources by adopting a consistent, innovative, focus during this initial stage before beginning quantitative approach. systematic coverage in October 1985. Table 8. Aerial photography used for the survey's mapping Sheet Runs Film no. Scale Date flown AJANA 4 WA2092 1 :50,000 28.09.82 BELELE 1,13,14 WA2308 1 :50,000 28.06.85 2-6 WA2309 1 :50,000 27.06.85 7-12 WA 2310 1 :50,000 28.06.85 BYRO 7 WA 2187 1 :65,000 13.12.83 8-10 WA2186 1 :65,000 13.12.83 CUE 1-4 WA2015 1 :50,000 28.10.81 5,6 WA2027 1 :50,000 16.12.81 7-14 WA 2011 1 :50,000 06.10.82 GLENBURGH 8-14 WA 2291 1 :50,000 19.03.85 KIRKALOCKA 1-3 WA 1841 1 :50,000 22.11.79 MURGOO 1-4 WA2015 1 :50,000 15.12.81 5-9 WA2027 1 :50,000 17.12.81 10-14 WA2028 1 :50,000 17.12.81 ROBINSON RANGE 7-11 WA2304 1 :50,000 01.06.85 12-14 WA2305 1 :50,000 01.06.85 YALGOO 1,2 WA2103 1 :50,000 05.12.82 38 A series of 209 pre-planned traverses (see Figure 30) pastoralists accompanied the survey team during was used, each generally 50 to 150 kIn long, to obtain some of the fieldwork on their leases and provided lines of ground access and proximity to sampling current information on aspects of station points and sites in each part of the area. infrastructure, management, history;. ecology and sociology. First hand experience of the local area and of the operational methods and approaches taken by the survey team was exchanged in this way. GLENBURGH ROBINSON RANGE Component techniques during fieldwork Land system mapping PrelirninarYf tentative boundaries and designations of land systems were identified and marked on aerial photographs, under stereo, before each traverse and subsequent ground truthing. Boundaries and designations were then modified in the field as necessary. After fieldwork was completed, the land system definitions were finalised and the entire land system classification of the area revised. The boundaries and designations of each land system polygon were revised accordingly and checked twice before mapping started. 100. kilometres Topographical and lease infrastructural updating (for Figure 30. Traverse routes, Murchison rangeland survey. pastoral lease plans) The total coverage achieved by the main survey During the fieldwork the position of station tracks, program included: fences and water points, previously identified on the aerial photographs in the office, were validated • 13,621 km of traverse and point assessments; wherever possible. Any anomalies were usually • 679 inventory sites; and resolved in consultation with the pastoralist I manager. New infrastructure developed after the aerial • 1289 condition assessment sites. photographs were taken was also positioned and Key features of the fieldwork included: marked on the photographs. " involvement of station managers/ owners As an adjunct to this rangeland survey, a separate wherever possible; survey program, to identify the boundaries of all leases within the area, was initiated by the 9 traverse coverage (point assessments, land Department of Land Administration in 1987. This system boundary definition and air photography entailed a thorough research of historical records of mark-up); previous lease definition and subsequent relocation and resurvey of many of the original survey markers. e sampling inventory sites; Leases previously unmarked were also physically • delineation of severely degraded and eroded defined and it is now possible to relate achlal areas; occupational boundaries (i.e. boundary fences) to administrative boundaries for the first time. G sampling condition sites; • identification and collection of geological, soil and plant specimens; Land system and unit description through inventory " collation of data and ad hoc reviews of sites cumulative progress; As a major part of field activities, basic land co referral to existing maps and literature; resource data were compiled from site observations collected at inventory sites. Each inventory site (I site) • maintaining a consistent photographic record. was pre-selected from aerial photographs as being Involvelnent of the pastoral community was a vital representative of a particular element of the photo part of the fieldwork, the total success of which would pattern. Generally, these elements of photo-patterns not have been possible without the continuous approximate to land units, or a recognisable part of. support and cooperation of individual pastoral land units on the ground. Figure 31 shows the 10catlOn families. In about two-thirds of all instances, of inventory sites within the survey area. 39 Sites were selected according to: • Pastoral lease name • aerial photo-pattern and land unit identification; • Date • the cumulative coverage of such sites achieved at • Compass bearing showing direction of oblique that time; ground photograph of site • the relative abundance of the type of photo Physical environment pattern or land unit within the broader land system; and • Slope (in per cent) • the degree to which the site was likely to have • Geology (according to the 1:250,000 Geological been subjected to grazing pressures, or other Survey series) known management (or envirorunental) impacts. • Site geology - if different to the above The location of each site was marked on the aerial • Surface mantle: abundance, shape, size and type photograph for future incorporation into the resource map base. The site itself was defined as an area within • Outcrop abundance and type 100 m radius of the photo-point if the land unit being • Accelerated erosional features and their extent sampled was> 200 m wide, or if smaller, was bounded (Table 11) by the physical boundaries of the unit. Site data were recorded on standard sheets (Appendix 4). • Vegetation condition rating (Table 10) Vegetation • Vegeta tion type GLENBURGH ROBINSON RANGE • Total projected foliar cover (PFC) by all canopies of perennial shrubs and trees . '. " . , '. • The dominant species and order of cover " .... .',. " ." -;. . .,.. dominance of each stratum of perennial '. . , " , ' .. vegetation '.. ; . , . . ,,' •'. { BYRQ • : BELELE. ~ . • Cover class for perennial grasses . ' ", " , ' ., .. ','. " . , . .. : ... .. • List of perennial plant species • ~ t. • •. .' ":' , · \ '. . .. ".. . '.\~' ..... , '. ". Soil ...... " , , ." . , .' : ,0, . '. In most cases both soil pit and auger observations were used to make profile descriptions. A grad uated . , '. "'~" ': . ': • *, CUE' .,...... soil auger of 5 em diameter was used to retrieve soil to ... . .:. \ .. ': ~ . a depth of 1 m or until underlying hard rock or •....., '. .: 't substrate was encountered. In conjunction with the · . ::', graduated auger, a pit up to 50 cm deep allowed boundaries for the upper layers of the soil to be described. kliomulr.1 Soil profiles were described using the techniques Figure 31. Inventory sites, Murchison rangeland survey. and standards given in the Australian Soil and Land Survey Field Handbook (McDonald et al. 1984) and by Northcote (1979). Technical data collected routinely at inventory sites were as below. Additional notes and sketches of site Soil textures were determined for the fine earth attributes and special features of interest were also « 2 mm) fraction after sieving out the coarse recorded. Such notes enable the recorder to recall (and fragments. The sieved fraction was moistened and the a reader to appreciate) particular aspects of the sites behaviour of the kneaded soil recorded. Soil textures much more clearly at a later date. were determined throughout the soil profile and used Logistics allowed up to one hour to make an to characterise the different layers. Data recorded inventory of soil, vegetation and landform at each site. included: General • Principal profile form (Northcote 1979) • Aerial photograph: year, map sheet, run and • Total soil depth number • Soil substrate • Site number • Soil surface type • Land system and unit • Observation method 40 • Horizon designation 100 m either side of the kilometre point. It was sometimes necessary to stop the vehicle and inspect • Depth the site on foot. • Texture Where traverses ran along fencelines, assessments • Colour (Munsell 1954) were made for the paddock adjacent to the track rather than across the fence. Two assessors were present to • Moisture resolve difficulties in assigning ratings to difficult or • Consistence unusual sites. • Fabric The definitions and numerical ratings for soil erosion and vegetation condition are shown in Tables 9 • Structure and 10 respectively. • Ped shape • Boundary distinction • Carbonate detection (by effervescence with dilute hydrochloric acid ) • pH (by field colorimetric method after Raupach and Tucker 1959) • Details relating to coarse fragments/soft segregations Point assessments of soil and vegetation condition during traverses The method involved continuous accurate positioning of the traverse vehicle while travelling Fenceline effects observed during traverses provided many along a mapped course, usually a station track, but in valu able examples of the impacts of different grazing where necessary across country or along a road. At management pressures and past events related to pastoral management. Here, a river saltbush community (near side of intervals of 1 krn the land title (lease name), paddock fence) has been succeeded by unpalatable shrubs such as name (if known), particular land unit and land system prickly wattle (Acacia victoriae) , desert hakea (Hakea arida) being crossed at the time was identified and noted. and poverty bushes (Eremophila spp.). Note the degraded, The soil stability or erosion status and vegetation unproductive soil surfaces conspicuous between the 'woody condition was then assessed over an area of up to weed' tall shrubs in the background. Table 9. Criteria for erosion ratings Severity Rating Comment Wind erosion Nil 0 No erosion. Minor Litter redistribution and sma ll scalds. Small isolated scalds on wh ich the surface shows some degree of polishing. Red istrib ution of soi l to the margins of the scald, or minor build up of so il material around obstacles. Moderate 2 Large isolated scalds and hummocks. Stripping of the soil surface and build up against obstacles associated with large but generally discontinuous scalds; or numerous small scalds scattered throughout the site. Severe 3 Major deflation of soil surface. Active stripping resulting in large continuous scalds with polished and sealed surfaces. Frequent large hummocks against obstacles. Major dune drift in sandy systems. Plant cover very sparse to absent. Water erosion Nil 0 No erosion . Minor Rilling or thin sheeting. Patchy rilling and small gullies affecting small areas or thin sheeting (1 to 2 cm) and breaking of the surface seal on parts on the site. Some redistribution of soil and litter downslope. Much undisturbed ground between affected areas. Moderate 2 Gullies and/or sheeting. Gullying on the lower slopes or more susceptible parts of the site, these being capable of extension to tess susceptible areas. The gullies may be associated with extensive but discontinuous disturbance of the soi l surface by sheet erosion and redi stribution of soil material, Severe 3 Terracing or extensive gullies . Severe sheeting or terracing affecting nearly all of the site. Redistribution of so il and exposure of subso il or rock material. The sheeting may be associated with or repl aced by very extensive gullying over most of the site. 41 Table 10. Criteria for vegetation condition ratings Rating Condition indicators Excellent or very good. For the land unit-vegetation type, the site's cover, structure and composition of shrubs, pe~ennial herbs and grasses is near optimal, free of obvious reduction in palatable species or increases in unpalatable species. 2 Good. Perennials present include all or most of the palatable species expected; some less palatable or unpalatable species may have increased, but total perennial cover is not very different from the optimal. 3 Fair. Moderate losses of palatable perennials and/or increases in unpalatable shrubs or grasses, but most palatable species and stability desirables still present; foliar Gover is less than on comparable sites rated 1 or 2 unless unpalatable species have increased. 4 Poor. Conspicuous losses of palatable perennials; foliar cover is either decreased through a general loss of perennials or is increased by invasion of unpalatable species. 5 Very poor. Few palatable perennials remain; cover is either greatly reduced, with a loss of the normal structural community and much bare ground arising from loss of stability desirables, or has become dominated by a proliferation of unpalatable species. Traverse assessment symbols on the 1:250,000 maps Assessment of vegetation and soil condition at Map symbols depicting both vegetation condition preselected 'condition sites' and soil erosion status were devised to depict land The quantitative approach used for such resource conditions simply and visually across the assessments represents a departure from previous maps of the area. regional rangeland surveys. Quantitative data were The design of the circular symbol (Figure 32) was collected at pre-selected sampling sites (C sites, a based on the central part of the symbol representing standard recording sheet is attached as Appendix 4) perennial vegetation and the outer part of the symbol throughout the survey area (see Figure 33), in order to representing the soil. characterise the full pattern of condition states and management-related changes within the major, Traverse points with vegetation in good condition productive land units. A further aim was to elucidate are represented by a small filled inner circle. Where the most powerful indicators of soil and vegetation soil surfaces were also in good condition, i.e. with no status. Indicators, whether qualitative or quantitative evidence of accelerated erosion, the outer zone of the in nature, would be of value in the diagnosis of circle is also filled, making the resulting symbol successful land conservation (in the absence of appear as a larger, circular spot. At the opposite end of change) on the one hand and in the evaluation of the condition spectrum, vegetation in poor condition change (towards desirable objectives in recovery from (unfilled inner circle) is associated with lost (severely degraded states) on the other. eroded) soil surfaces, which are depicted by a disintegration of the outer circle. The condition site approach was designed during the reconnaissance survey fieldwork to investigate The intermediate states of condition for both various site attributes which could be reasonably vegetation and soil surfaces are thus depicted as part hypothesised as likely key variables of cumulative filled inner and outer circles, in accordance with the pastoral management impact, and to reflect states of combinations of condition status indicated by the two condition in the long term (rather than seasonal) sense. way table in the map key. Major considerations in the design of the field methods were: TRAVERSE ASSESSMENT SYMBOLS 1. time-efficiency to enable reasonable samples of VEGETATION CONDITION equivalent sites to be accumulated over the course of the major survey; 2. stratification in relation to pastoral management Good Fair Poor infrastructure, in order that particular null hypotheses (e.g. no difference in an attribute in Z relation to grazing distance from a stock watering Nil 0 Q point) could be tested to elucidate effects related to (f) e 0 0 pastoral management impacts; and tY Minor w Q 0 3. addressing the scale of within-site environmental --' patterning realistically, so that quantitative data 0 Moderate collected would be truly representative of the (f) • (() ~ ~ vegetation type and land unit in that part of a paddock or other management unit. Severe '::::.110 Five quantitative methods were developed to The more "lied the symbol. the belter the condItIon investigate specific vegetation types. Many vegetation types were sampled during the survey, with great Figure 32. Traverse assessment symbols, Murchison disparities in the numbers of sites eventually sampled rangeland survey. for each type. Summary quantitative data are 42 presented for 14 of the major vegetation types for Method A - Aggregated understorey communities which useful sets of data and condition states have (for vegetation type Stony Snakewood Shrubland) been characterised. Ten canopies of tan shrubs/low trees were sampled Each condition site was preselected on aerial (along a line of nearest neighbours) across the very photographs to provide a sample of a well-developed scattered to scattered tan shrub landscape. major land unit at which an internally consistent Understorey shrubs and perennial herbs under each example of a major and pastorally productive canopy were counted and recorded, and any presence vegetation type could be expected. All sites were of palatable perennials in inter-canopy areas was selected at controlled distances from the nearest noted. accessible stock water point (I, 2, 4 km ± 10% or> 5 km). Water points included those which were in one Method B - Chenopod steppes way or another malfunctioning, turned off, disused or derelict at the time they were encountered as well as For vegetation types: those actually delivering water to stock. All developed • Saltbush Shrubland; water points were therefore considered to have had the capacity to have been focal points for grazing use. • Bluebush Shrubland; Other data collected at all sites included the • Mixed Halophyte Shrubland; following. • Samphire Shrubland; and (i) General • Mulga Chenopod Shrubland (part). Aerial photograph: year, map sheet, run and number. A plotless cover ranking of species, whereby the AMG coordinates. shrub species contributing the highest amount of Land system and unit. cover (as PFC) was allocated a ranked score of 1.0, the Pastoral lease name. next most prominent species 2.0 and so on. Species Pasture (~vegetation type). with similar cover contribution which could not be Paddock name. easily discriminated on the ordinal scale of ranks were Quadrant of paddock (NW, NE, SE, SW). scored as being equal and afforded values that were Site method (A-E, see below). Quadrat area sampled (for methods C and D). arithmetically equal in sum to what those ranks would have totalled if scored without ties. For example, two Total projected foliar cover (PFC) by all canopies of co-dominant species score 1.5 each; three equal perennial shrubs and trees. 'runners up' behind a clearly dominant species (score The dominant species and relative cover dominance of 1.0) would each score 3.0 [(2 + 3 + 4) + 3]. Score values each stratum of perennial vegetation. up to 9.5 were recorded where applicable. (ii) Vegetation assessment Method C - Very sparse shrub communities For vegetation types: • Stony Mulga Mixed Shrubland; GLENBURGH ROBINSON RANGE • Hardpan Mulga Shrubland (minority of sites); .' , .' and I • ~ t ..... ,'r . ..; .,: " .. .; .~ ", ' . • Mulga Chenopod Shrubland (minority of sites). . .. , . .. ,' . ", . " '. " '" . , " • • + ," A belt transect census technique was used whereby /'.... . ' . . .. a 10 m rope was stretched out and carried by two ... • ". # ,'.', ... ,' *. ~.. ." ,01," ".," _:1": ,f' .... "~'''~. ' \: '-:. 0'. " observers for 100 m in a set direction (i.e. along a j .:: .t...... SYRp... :.· ~ ..••• .BE~ELE .. 1 ',j' • transect line from the photo point) and again along a :. '!.:':: :.:-,' , . :.':" '.. ::. ',....+: " :.~" ... n'...... :.' '. parallel line on return. The transect area sampled was . :' •••• ' -~ t "I, .,' + " I. " .' ...... ' ... ':"':'~. thus normally 2000 m' by this technique, which was ". • • • ' .. ',... I I " '." . '. '. " able to address the composition of very scattered and/ ...... ' J; '.f • . ,. or irregularly clumped non-halophytic shrubland s. In : .. • \' 0' ,* I ." . " ':' .:" • :"/', : ••: ••: •••• {,.... ~.'•• : , : practice, a third observer walking behind the rope ...... + . :.~ . ~\ . :~ .:'.,' ... : ': .1 ...... ': ... . ~ ... ' , ...... '.: ..• identified and scored all perennial plants in the , '.. \ ' : ".,".,:,: ,,'.' : .. ' # transect area, with the assistance of both rope carriers. • ,," f '.,t ,.Mu.aqob: :.:' \ .. ~ ~C·UE ... \·. . , ...... - .#: '. - ~ Transect length was verified by a cotton thread ,,,.'.1 ,,, .~! \ ; ....: •.: 't' : •• ..:: ".. . • ...... /. ': ', ' measuring device...... , ' . I ••,...... : ... f ." .. ' ..' .... '. . '-_"U' '. f.. ,-r----'-l--...... :.:•. t" ; ... Method D - 'Mulga communities' .' " : For vegetation types: • Hardpan Mulga Shrubland; kilometres • Granitic (and other) Mulga Shrubland; Figure 33. Condition assessment sites, Murchison range land survey. • Mulga Chenopod Shrubland; 43 • Riverine Mixed Shrub land; and number of woody perennial species 25 ~------, • Sand plain Acacia Shrubland. A two-plot quadrat census technique was used to sample two square patches of vegetation (each 500 m' ) one positioned to be representative of less dense 15 or ~ter-clump vegetation and the other to be representative of higher cover patches within 100 m of 10 the site photo point. In this way the effect of plot 5 position in commumhes exhlblt1ng some de~ ree of tall shrub patterning or grovmg could be ffiuuffil sed. The total area of the quadrats used (1000 m' ) was o 500 100) 1500 200J 2500 3COO 3500 4O'XI 4SOO 500J standardised after reconnaissance survey and quadrat area (sq m) construction of a species-area curve for sites in 'fair to good' condition (F igure 34). Figure 34. Calibration of quadrat sampling areas by species area curve for Hardpan Mulga Shrubland (HPMS) in 'fair to good' condition. Method E - 'Perennial grasslands' For vegetation types: • Calcrete Shrubby Grassland; A plotless cover-rank technique was used. The total cover of perennial grasses on the site was assessed by • Non-calcareous Shrubby Grassland; photographic reference class. As with method B for • Alluvial Tussock Grassland; chenopod steppes, a plotless cover ranking of species was scored by the cover rank score method. • Wanderrie Bank Grassy Shrubland; and • Sandplain Wanderrie Grassy Shrubland. (iii) Soil condition assess ment Any soil surface degradation and evidence of erosion encountered at each site was assessed by the combined type intensity scale (after Anon. 1988) detailed in Table 11. The scale combines an assessment of the proportional area of a site affected by surface degradation and soil redistribution with alternative criteria for the type of erosion observed at each level of areal intensity. More than one sub-class could be recorded for any particular site, but by definition only under one areal intensity class. In this way, the.sites p rovided a spot sampling record of the area of land surface affected and the major symptoms, features and types of erosion encountered. Quantitative sampling methods were devised for the major vegetation types. Low-density shrublands required large transects (0. 1-0.2 hal either marked for width using a 10 m length of rope, or as pegged cens us plots (below). The in cidence, type and areal severity of soi l erosion encountered throu ghout the su rvey was assessed by the type intenSity scale at every site sampled. Another, simpler system of eros ion assessment was used to record observations during each vehicular traverse. 44 Table 11. Combined type intensity ratings for wind and water erosion Type intensity combination Rating No accelerated erosion present 00 Slight erosion « 1OOk of site affected) Slight accumulation of wind blown soil around plant bases and other obstacles 11 and/or Removal of finer soil particles evident but soil crust is largely intact 12 and/or Occasional rills « 300 mm deep) evident 13 and/or A few scalds present, usually less than 2 m in diameter 14 Minor erosion (10-25% of Site affected) Accumulation of soil around plant bases with plant mounds noticeably enlarged 21 and/or Evidence of pedestalling but soil loss minor and plant bases not greatly elevated 22 and/or Breaking of surface crust with small erosion faces and some redistribution of soil 23 and/or Rilling evident but no gully development 24 and/or Scalding evident but scalds relatively small and discontinuous 25 Moderate erosion (25-50% of site affected) Wind piling around plant bases and other obstacles is common but no plants completely covered 31 and/or Pedestalling apparent with plant bases distinctly raised and with obvious soil loss 32 and/or Rilling common or gullying present on parts of site 33 and/or Suriace sheeting with erosion faces, (and/or microterracing) and active redistribution of soil 34 and/or Wind scalds common 35 Severe erosion (50-75% of site affected) Extreme hummocking around plants and other obstacles: some plants completely covered 41 and/or Severe pedestalling with plant bases greatly elevated and major soil loss 42 and/or Widespread rilling or major gullying 43 andlor Scalding extensive, smaller scalds have coalesced to form large, more or less continuous scalded areas 44 and/or Surface sheeting with extensive exposure of subsoil or parent material; erosion faces 45 (~nd/or microterracing) and active redistribution of soil and/or Much of suriace generally unstable with ripple mark formation 46 Extreme erosion (75-100% of site affected) General suriace movement, total surtace area bare with formation of shifting dunes 51 and/or Surtace sheeting and/or scalding complete with exposure of subsoil or parent material 52 and/or Extensive gullying 53 Delineation of areas of severe degradation More than 90% of areas indicated as being severely and erosion degraded and eroded by air photographic evidence were visited on the ground to verify the finding and to In most instances, eroded soil surfaces on the red delineate actual boundaries of the affected area. soil types are highly reflective in the red end of the Confirmation of the state of a few unseen areas was visible spectrum. Where the particular patch or 'cell' given by managers and other people with local of erosion is sufficiently large (> 5 hal, it was usually knowledge. In this way, the total depiction of major conspicuous and distinctive on aerial photography, severely degraded and eroded areas presented on the especially where the erosive process leaves laminar map series attempts to present a complete picture for shaped sandy residuals and sinuous scour lines across the region, rather than a sampling approach. broadly scalded and sheet-deflated areas. In some instances, extensive mantling of lag gravels and other surface features served to mask the visibility of eroded Analysis of the field data areas, on both aerial photographs and satellite images. Inventory site data Elsewhere, unusually reflective uneroded surfaces (e.g. quartz-mantled plains) mimic the signatures of The inventory site data were sorted and eroded areas, particularly where the perennial summarised on a land unit, land system, vegetation vegetation is degraded or mainly lost. and soil basis using the INF09 data base system on 45 16602--4 the Prime computer and various database packages on ~<; 0 .... 0 ... 0 personal computers at the Department of Agriculture. ~&. '" "' This information was used to draw up detaIled land unit, land system, soil type and vegetation . <; In -0 0 0 .... descriptions which are presented later thIS report. ~ 0 "'... 0 l-a.. '" '" ~ ~ e '" '" 0 ig .1ij 0 0 Condition site data eLL :;;: ... 0 "''" "' '" 0 '" Data obtained from condition sites were sorted and e .2 '0 analysed by several different methods on PRIME and E g 0 0 en 0 personal computers. A small number of sites were 1l,CJ "''" ~ :g reclassified for vegetation type after critical re ~-g examination of their biophysical attributes. In a few 0 0 ~ 0 :%!& '" '" cases, where site attributes were inconsistent with those of initially allocated vegetation types, or land > 0 0 0 0 ~ unit definitions, they were excluded from subsequent ~ (f)" '" analysis and summaries of key criteria. Such sites are indicated by the suffix 'x' on the vegetation type "0 0 0 0 ... designation (see Appendix 5). -0 ~ ~~ '" "' C e o 0 'in Traverse record e e 0 0 en 0 ~ " .- "' '" Data recorded as hard copy in the field were .. ]j~ '" C {? checked and re-checked against final land system o delineations and individual point locations on aerial C 0 0 0 .... o Z 0 ~ 0 0 photographs. Hard copy records were then entered ~ ~ '" ~ E '" '" and verified in a database, from which summaries and sortings of condition assessments were obtained for > 0 0 0 0 ~ each: f (f)" '"~ "C • land system, unit by unit; .!!! "0 0 0 0 0 ... • lease and land system/unit within each lease; .. ~ "' C -:. '" o .s • and for the whole survey area. ~ e .S! .2 0 0 en 0 Where accelerated erosion had been recorded from ui '"e e "' ~~ '" '" observation of wind or water erosion symptoms, total 1il" erosion was derived by combining the wind and water i :;: erosion traverse recordings into one figure, with ~ 0 en 0 0 .... Z 0 ... 0 0 default to the higher recording. Table 12 shows an ~ ~ '" ~ '~ '" '" example condition statement derived from traverse records for one land system (and its component units) > ~ 0 0 0 0 0 0 on one station. (f)" ,g-E "0 -0 0 0 0 0 0 0 ~:2 Map preparation "~ e .;: 0 .. 'ine Appendix 6 of this report consists of six 1:250,000 ..: "0 .-e 0 0 0 0 ~ scale maps which graphically illustrate the various " " ~ C e:' '" components of the survey. These types of maps are ..E ~ generally referred to as thematic maps meaning that they are designed to depict a particular theme or 0 .... 0 0 0 en Z 0 0 0 0 en ~ ~ '" ~ ~ ~ themes and are therefore not necessarily fully C comprehensive in showing all data relevant to the .51 survey area. For instance they do not show all :t: '" ~ ~ topographic detail such as fences and minor tracks. 'C 'O"E .... 0 "o ·8 '" '" '" ~ The limitations of scale therefore should be considered (J Zo "~ '" '" whenever the maps are used. Other, more specific map "ii.. series are available from various sources which will c; .e E E 0 ,. 0;" e 0= e complement this series . 0; " .,. 0. In .0 0> 0. e i '">, " As a compromise between scale and the amount of ~ .~ >, 0. " E "0 e e '" '" '" e .~'" ~ <2 detail that could have been shown on the 1:250,000 ..~ ~ ~ >, (f)'" 0 &l I .3 maps a format was devised that would reasonably .. * E "0 '" :0 '" ~ accommodate as much of the survey data as was e E e ;g E ~ '" ''E ~ ~ 5 ~ ~ ~ ~ ~ (f) necessary to convey a regional perspective of the area. 46 The traverse assessments have been shown on the operations (Ed. RB. Hacker). Deparhnent of Agriculhrre, maps as a series of symbols derived from the traverse Western Australia. data. Beard, J.S. (1976). Vegetation survey of Western Australia, Murchison 1:100,000 vegetation series - Explanatory notes to The maps depict the following major themes. sheet 6. University of Western Australia Press. Bettenay, E., Churchwood, HM. and McArthur, W.H. (1967). Cultural data Explanatory data for sheet 6, Meekatharra - Hamersley Range area. Atlas of Australian Soils, CSIRO, Melbourne University • Cadastral or property boundaries and identifiers. Press. • Topographic infrastructure - roads, watering Christian, e.S. and Stewart, G.A (1953). General report on survey of Katherine-Darwin region 1946. CSIRO Land Research Series points, towns, homesteads. No. 1. • Topographic features - lakes, rivers, creeks and Christian, e.S. and Stewart, G.A (1968). Methodology of integrated ranges. survey. Aerial surveys and integrated studies, UNESCO, Paris, pp. 233-280. Churchwood, H.M. and McArthur, W.H. (1967). Explanatory data Resource data for sheet 6 Meekatharra-Hamersley Range area, Atlas of • Land systems and land types. Australian Soils. CSIRO, Melbourne University Press. Curry, P.J. and Payne, AL. (1989). Rangeland surveys: a basis for • Severely degraded and eroded areas (sde). improved land use. Journal of Agriculture, Western Australia 30: 111-115. • Inventory sites. Geological Survey of Western Australia (various authors and dates). • Condition sites. Explanatory notes 1:250,000 Geological series: • Point traverse assessments. Glenburgh sheet Robinson Range sheet These and other components are permanently Byro sheet archived on various levels within a computer (digital) Belele sheet mapping system and therefore allow great flexibility Murgoo sheet in the manipulation of this data to produce specific Cue sheet plans tailored for selective applications. A pastoral Mabbutt, J.A, Litchfield, W.H., Speck, N.H., Sofoulis, J., Wilcox, lease map for each station has been prepared at a scale D.G., Arnold, J.M. and Wright, RL (1963). General report on of 1:100,000 and contains all the information shown on lands of the Wiluna-Meekatharra area, Western Australia the published 1:250,000 scale series but with more 1958. CSIRO Land Research Selies No.7. detail of hydrological features and station McDonald, RC., Isbell, RF., Speight, J.G., Walker, J. and Hopkins, infrastructure. M.S. (1984). 'Australian soil and land survey field handbook'. Inkata Press, Melbourne and Sydney. The major advantage of computer mapping is that changes and updates can be readily made. This facility Mitchell, A.A., McCarthy. R and Hacker, R.B. (1979). A range inventory and condition survey of part of the Western also enables changes to station infrastructure (such as Australian Nullabor Plain, 1974. Department of Agriculture, re-positioning of fences and mills) to be modelled and Western Australia, Technical Bulletin No. 47. the management implications of the changes to be Munsell Color Co. (1954). Soil color charts. Munsell Color Co., assessed. Baltimore, USA. Northcote, KH. (1979).' A factual key for the recognition of Australian soils, 4th edition'. Rellim Technical Publications Pty Ltd, Glenside, South Australia. Presentation of preliminary findings for Payne, AL., Kubicki, A, Wilcox, D.G. and Short, L.e. (1979). A the survey to the Murchison pastoral report on erosion and range condition in the West Kimberley community area of Western Australia. Department of Agriculture, Western Australia, Technical Bulletin No. 42. In recognition of the fact that the pastoral Payne, AL., Mitchell, AA, and Holman, W.F. (1982). An inventory community needed to have early access to, and and condition survey of rangelands in the Ashburton River awareness of, the main patterns of survey findings, a catchment, Western Australia. Department of Agriculture, preliminary presentation of results was made at a Western Australia, Technical Bulletin No. 62. public meeting hosted by the Murchison Land Payne, AL., Curry, P.J. and Spencer, G.F. (1987). An inventory and Conservation District (and attended by members of condition survey of rangelands in the Carnarvon Basin, the Meekatharra, Yalgoo, Cue and Mount Magnet Western Australia. Department of Agriculture, Western LCDCs) on 11 May 1989. The meeting made a series of Australia, Technical Bulletin No. 73. resolutions concerning ways to use the survey Payne, AL. and Tille, PJ. (1992). An inventory and condition survey information and combat land degradation through of the Roebourne Plains and surrounds, Western Australia. management. Department of Agriculture, Western Australia, Technical Bulletin No. 83. Raupach, M. and Tucker, B.M. (1959). The field determination of soil reaction. Joumal of Australian Institute of Agricultural Science References 25,129-33. Wilcox, D.G. and McKinnon, E.A (1972). A report on the condition Anon. (1988). The Western Australian rangeland mOnitoring system of the Gascoyne catchment. Deparhnent of Agriculrure, for arid shrublands.lnstrudion manual, Part I, Field Western Australia. 47